System for using a two part cover for protecting a reticle

ABSTRACT

A system and method are used to protect a mask from being contaminated by airborne particles. They include providing a reticle secured in a two-part cover. The two part cover includes a removable protection device used to protect the reticle from contaminants. The cover can be held inside a pod or box that can be used to transport the cover through a lithography system from an atmospheric section to a vacuum section. While in the vacuum section, the removable cover can be moved during an exposure process during which a pattern on the reticle can be formed on a wafer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Appl. Nos. 60/414,358, filed Sep. 30, 2002, 60/358,354 (“the'354 Prov. App.”), filed Feb. 22, 2002, and 60/364,129 (“the '129 Prov.App.”), filed Mar. 15, 2002, which are all incorporated by referenceherein in their entireties.

This application is related to co-pending U.S. application Ser. No.10/369,108, filed concurrently herewith, which is incorporated bereference herein in its entirety.

This application is also related to U.S. Pat. No. 6,239,863 (“the '863patent”), which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to lithography, and more specificallyto the protection of lithographic reticles without the use of apellicle.

2. Related Art

Lithography is a process used to create features on a surface of asubstrate. The substrate can include those used in the manufacture offlat panel displays, circuit boards, various integrated circuits, andthe like. A semiconductor wafer, for example, can be used as a substrateto fabricate an integrated circuit.

During lithography, a reticle is used to transfer a desired pattern ontoa substrate. The reticle can be formed of a material transparent to alithographic wavelength being used, for example glass in the case ofvisible light. The reticle can also be formed to reflect a lithographicwavelength being used, for example extreme ultraviolet (EUV) light. Thereticle has an image printed on it. The size of the reticle is chosenfor the specific system in which it is used. A reticle six inches by sixinches and one-quarter inch thick may be used, for example. Duringlithography, a wafer, which is disposed on a wafer stage, is exposed toan image projected onto the surface of the wafer corresponding to theimage printed on the reticle.

The projected image produces changes in the characteristics of a layer,for example a photoresist layer, deposited on the surface of the wafer.These changes correspond to the features projected onto the wafer duringexposure. Subsequent to exposure, the layer can be etched to produce apatterned layer. The pattern corresponds to those features projectedonto the wafer during exposure. This patterned layer is then used toremove exposed portions of underlying structural layers within thewafer, such as conductive, semiconductive, or insulative layers. Thisprocess is then repeated, together with other steps, until the desiredfeatures have been formed on the surface of the wafer.

As should be clear from the above discussion, the accurate location andsize of features produced through lithography is directly related to theprecision and accuracy of the image projected onto the wafer. The rigorsof sub-100 nm lithography place stringent demands not only on thelithography tool, but also on the reticle. Airborne particles and dustthat settle on the reticle can cause defects on the wafer. Small imagedistortions or displacements in the reticle plane can be larger thancritical dimension and overlay error budgets. A conventional solution isto use a thin piece of permanently fixed transparent material as apellicle for the reticle.

This pellicle remains in place during all stages of the lithographyprocess. A pellicle has a dual role in improving the accuracy of theimage projected onto a wafer. First, a pellicle serves to protect thereticle from direct contact with particulate contamination. As discussedabove, particles that settle on the reticle can produce imagedistortion, so they must be removed. However, removal of particles fromthe reticle can cause damage to the reticle because such removal mayinvolve direct contact with the reticle. When a pellicle is used,particles will settle on the pellicle rather than the reticle. Thus, itis the pellicle that must be cleaned. Cleaning the pellicle rather thanthe reticle poses fewer dangers to the integrity of the reticle sincethe reticle is protected during this cleaning by the pellicle itself.

The second role played by a pellicle is related to the standoff of thepellicle. During exposure, the focal plane corresponds to the locationof the image printed on the reticle. By including a pellicle, anyparticles in the system will settle on the pellicle rather than thereticle. By virtue of the thickness of the pellicle, and thus thedistance between the surface of the pellicle and the patterned surfaceof the reticle, these particles will not be in the focal plane. Sincethe pellicle lifts the particles out of the focal plane, the probabilitythat the image projected onto the substrate will include these particlesis greatly reduced.

This solution discussed above works well in many conventionallithographic processing techniques. Thus, use of such a system isconvenient in a system in which light passes through both the reticleand the pellicle because materials are available for producingtransparent pellicles and reticles. The pellicle approach, however, isnot well suited for use in EUV applications because the shortwavelengths of light being used are easily absorbed when transmittedthrough gases or solids.

Therefore, currently there are no materials sufficiently transparent toEUV that can be used to make a pellicle. In EUV lithography, the EUVdoes not pass through the reticle, but is reflected off the image sideof the reticle. This technique is known as reflective lithography. If apellicle were to be used in a reflective lithography process, the EUVwould necessarily pass through the pellicle twice, once on the way tothe reticle and again after reflecting off of the reticle. Thus, anyamount of light loss associated with the pellicle is effectively doubledwith EUV processing techniques.

Therefore, what is needed is a system and method that allow forprotection of a reticle from contaminants that do not substantiallyreduce the quality of EUV light passing through the system.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention provide a method for transporting amask, including the steps of: (a) covering a first portion of a maskwith a removable particle cover creating a mask-cover arrangement (b)enclosing the arrangement inside a gas-tight box, having a mask-carryingportion and a lid, separable from the mask-carrying portion, and (c)transporting the arrangement inside the box.

Embodiments of the present invention provide a gas-tight box fortransporting a mask, including: a mask-carrying portion, a lid, a gassealing device, for preventing gas flow between the mask-carryingportion and the lid, and a latch, for temporarily attaching and securingthe lid to the mask-carrying portion.

Embodiments of the present invention provide a method for transporting,handling and processing a mask, including the steps of: (a) covering afirst portion of a mask with a removable particle cover creating amask-cover arrangement, (b) enclosing the arrangement inside a gas-tightbox, having a mask-carrying portion and a lid, separable from themask-carrying portion, (c) transporting the box containing thearrangement to a process tool, having at least one of each of thefollowing components: a de-podder, a mini-environment chamber, amini-environment manipulator, a loadlock, a vacuum chamber, a vacuummanipulator, and a mask mount, (d) placing the box containing thearrangement on a first opening of a de-podder, such that the lid of thebox prevents gas flow through the first opening, (e) purging theinterior of the de-podder with clean gas, (f) opening the box byseparating the mask-carrying portion from the lid, keeping the lid inplace, for blocking gas flow, and moving the mask-carrying portion andthe arrangement to the interior of the de-podder, (g) extracting thearrangement from the de-podder through a second de-podder opening into amini-environment chamber, using a mini-environment manipulator andplacing the arrangement inside a loadlock through a first loadlockopening, (h) pumping down the loadlock, (i) extracting the arrangementfrom the loadlock through a second loadlock opening and moving thearrangement to the interior of a vacuum chamber, using a vacuummanipulator, (j) placing the arrangement on a mask mount, such that theuncovered portion of the mask is in contact with the mount, (k) holdingthe mask with the mount, (l) separating the cover from the mask andtaking away the cover, using the vacuum manipulator, and (m) processingthe mask.

Embodiments of the present invention provide a loadlock including: anenclosure having at least two openings, an atmospheric-side gate valvecoupled to a first opening of the enclosure, a vacuum-side gate valvecoupled to a second opening of the enclosure, a mask holder forreceiving a mask, located inside the enclosure, a movable dome forcovering the mask, located inside the enclosure, and a dome actuator formoving the dome, such that the dome can be positioned to cover the mask.

Embodiments of the present invention provide a method for transitioninga mask from atmospheric pressure to vacuum in a loadlock, including thesteps of: (a) placing a mask inside a loadlock, (b) covering the maskwith a dome to prevent airborne particles in the loadlock from reachingthe mask, (c) closing the loadlock, (d) pumping down the loadlock, (e)opening the loadlock to vacuum, (f) uncovering the mask by withdrawingthe dome, and (g) removing the mask from the loadlock.

Embodiments of the present invention provide a method for transporting,handling and processing a mask, including the steps of: (a) enclosing amask inside a gas-tight box, having a mask-carrying portion and a lid,separable from the mask-carrying portion, (b) transporting the boxcontaining the mask to a process tool, having at least one of each ofthe following components: a de-podder, a mini-environment chamber, amini-environment manipulator, a loadlock, a vacuum chamber, a vacuummanipulator and a mask mount, (c) placing the box containing the mask ona first opening of a de-podder, such that the lid of the box preventsgas flow through the first opening, (d) purging the interior of thede-podder with clean gas, (e) opening the box by separating themask-carrying portion from the lid, keeping the lid in place, (f)extracting the mask from the de-podder through a second de-podderopening into a mini-environment chamber, using a mini-environmentmanipulator and placing the mask inside a loadlock through a firstloadlock opening, (g) pumping down the loadlock, (h) extracting the maskfrom the loadlock through a second loadlock opening and moving the maskto the interior of a vacuum chamber, using a vacuum manipulator, (I)placing the mask on a mask mount, and (j) processing the mask.

Embodiments of the present invention provide a machine for processingmasks transported to and from the machine inside boxes, including: afiltered air environment portion, at least one atmospheric manipulator,at least one de-podder, a gas mini-environment portion, purged withclean gas at substantially atmospheric pressure, at least onemini-environment manipulator, at least one loadlock, a vacuum portion,and at least one vacuum manipulator.

Embodiments of the present invention provide a system including areticle and a cover coupled to the reticle to protect the reticle. Thecover includes a frame and a movable panel that moves to allow directaccess of light to the reticle during an exposure process. The reticleand cover are moved to a stage using a robot gripper. The reticle andcover may be coupled to a baseplate before being moved.

Further embodiments, features, and advantages of the present inventions,as well as the structure and operation of the various embodiments of thepresent invention, are described in detail below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the pertinent art to makeand use the invention.

FIG. 1 is an exploded diagram of the two-part cover in position on areticle according to an embodiment of the present invention.

FIG. 2 is a diagram showing the reticle in the two-part cover beingloaded onto the stage by a robot according to an embodiment of thepresent invention.

FIG. 3 is a diagram showing the reticle being exposed for lithographyaccording to an embodiment of the present invention.

FIG. 4 is an extrapolated diagram illustrating in relief the two-partover according to an embodiment of the present invention.

FIG. 5 is a method of alignment and transfer using the two-part coveraccording to an embodiment of the present invention.

FIGS. 6A and 6B are diagrams showing the registration features accordingto an embodiment of the present invention.

FIG. 7 is an extrapolated diagram illustrating in relief the two-partover with registration features according to an embodiment of thepresent invention.

FIG. 8 is a method of reinforcement for areas in the reticle, accordingto an embodiment of the present invention.

FIGS. 9-10 show a top and a bottom view, respectively, of an examplereticle cover according to embodiments of the present invention.

FIG. 11 shows exploded views of the reticle cover of FIGS. 9-10.

FIG. 12 shows a double wrap pod concept according to embodiments of thenpresent invention.

FIG. 13 shows an exploded view of the double wrap pod in FIG. 12.

FIG. 14 shows a loadlock according to embodiments of the presentinvention.

FIG. 15 shows an exploded view of the loadlock in FIG. 14.

FIG. 16 shows a reticle handler core according to embodiments of theresent invention.

FIG. 17 shows an entire reticle handler according to embodiments of thepresent invention.

FIG. 18 shows a flowchart depicting a method for transporting a maskaccording to embodiments of the present invention.

FIGS. 19A and 19B show a flowchart depicting a method for transporting,handling and processing a mask according to embodiments of the presentinvention.

FIG. 20 shows a flowchart depicting a method for transitioning a maskfrom atmospheric pressure to vacuum in a loadlock according toembodiments of the present invention.

FIG. 21 shows a flowchart depicting a method for transitioning a maskfrom vacuum to atmospheric pressure in a loadlock according toembodiments of the present invention.

FIG. 22 shows a flowchart depicting a method for transporting, handlingand processing a mask according to embodiments of the present invention.

The present invention will now be described with reference to theaccompanying drawings. In the drawings, some like reference numbersindicate identical or functionally similar elements. Additionally, theleft-most digit(s) of most reference numbers identify the drawing inwhich the reference numbers first appear.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Overview

Embodiments of the present invention provide a cover for protecting thereticle that is improved with respect conventional systems. Otherembodiments of the present invention provide a pod or reticle transportbox, compatible with the cover, which further protects the reticleagainst particles. Still other embodiments of the present inventionprovide a loadlock, compatible with the cover, which further protectsthe reticle against particles when transitioning the reticle betweenatmospheric pressure and vacuum. Still further embodiments of thepresent invention provide a reticle handler having three separateenvironments (e.g., filtered room air, gas purged mini-environment, andvacuum) with each environment being best suited for cost-effectivelyreducing the contamination of the reticle for its respective handlingsteps. Even further embodiments of the present invention provide amethod for handling the reticle with all of the above that minimizesreticle contamination.

Lithography has traditionally relied on a pellicle to protect thepatterned area of the reticle from particulate contamination. However,as discussed above, the absence of pellicle materials that aretransparent to Extreme Ultra Violet (EUV) light precludes this approach.In addition, the limitations of internal alignment make removal of theentire reticle cover difficult to correct. Therefore, according toembodiments of the present invention, a reticle is protected by areticle cover that includes a frame for supporting the reticle and apanel that can be removed during exposure and cleaning.

While lithography systems operate in clean environments, particles aregenerated during processing. These particles may contaminate thereticle. The reticle is periodically cleaned such that the particulatelevel on the reticle remains below an allowable threshold. It is thusnecessary to consider the sources of particle generation within alithographic system. Typically, particles within an otherwise cleansystem are generated as a result of friction. In conventional systems,particles are generated when reticles are transferred from one place toanother. Since in conventional systems it is possible for the reticle toslide during transport, additional particles may be generated as aresult of any reticle sliding during transport. Finally, vibration inconventional systems also causes friction and associated particlegeneration.

According to embodiments of the present invention, positional locatorsand ridges on the removable cover are included to eliminate transfer andreticle sliding friction. However, cover attachment and removal canproduce friction. Likewise, vibration, as in conventional systems, alsocontributes to particle formation. Thus, these differences in the causesof particle generation have been considered when implementing theembodiments of the present invention.

In addition to particle generation, particle settling is also aconsideration when designing a lithographic system. The use of aremovable panel in the embodiments of the present invention eliminatesthe opportunities for particles to settle onto the reticle at all times,except during the exposure step. Significant particle settling occurs attimes other than during exposure, thus the use of a removable panelaccording to embodiments of the present invention provides significantprotection to the reticle from particle settling even though the coveris removed during exposure steps.

Finally, particle migration must also be considered. Particle migrationoccurs during turbulence caused by fast motions and quick pressurechanges. In the EUV systems, many of the movements occur in a highvacuum environment. Thus, turbulence during movements from, for example,a library shelf to a projection mount is minimal. However, pressurechanges are involved, so this source of turbulence must be considered.Therefore, according to embodiments of the present invention, thisadditional source of particle migration is substantially eliminatedthrough the use of a removable panel coupled to a frame that is set tothe reticle.

Two Part Cover and Pseudo-Kinematic Registration of Same

FIG. 1 illustrates an exploded view of system 100 including a two-partcover 102 according to an embodiment of the present invention. Two-partcover 102 includes a frame 2, which supports a reticle 1 during handlingand remains in contact with reticle 1 and a stage 7 during exposure.Frame 2 includes an opening 14 that can be larger than a field ofreticle 1 to allow actinic light to pass through opening 14 during anexposure process. Frame 2 also includes an attachment device 8, whichcorresponds to attachment device 9 coupled to stage 7. Thus, attachmentdevice 8 allows frame 2 to be held by attachment device 9 on stage 7.

This embodiment also includes a panel 3, which is separated from frame 2just prior to lithographic exposure and re-attached to frame 2 justafter lithographic exposure. Panel 3 can be made from a material that istransparent to visible light to allow visual inspection andidentification of a front side of reticle 1.

Attachment devices 8 and 9 are shown between stage 7 and frame 2, aswell as between frame 2 and panel 3. Feature pair 5 a and 5 b can beincluded, as illustrated, between stage 7 and frame 2. Feature pairs 5 aand 5 b can be “between pieces,” which, as one skilled in the relevantart(s) would recognized based on at least the teachings describedherein, can be selected from a group including magnets and magnetictargets respectively in each piece, mechanical fasteners, such asspring-loaded latches or bi-stable latches in one piece and matchingtabs in the other piece, and gravity dependent devices, such as restingfeatures located in one piece on mating features located in the otherpiece.

According to embodiments of the present invention, attachment devices 8and/or 9 can have the following design criteria including, but notlimited to: a) attachment devices 8 and/or 9 can be detachable bydevices external to two-part cover 102, which can be located in a robotgripper 4 that loads reticle 1 onto stage 7, or in stage 7 itself,and/or; b) the release and reattachment of attachment devices 8 and/or 9should produce minimal contamination particles in order to avoidcontaminating reticle 1 (for this purpose, non-contacting devices can beused to actuate attachment devices 8 and/or 9 are preferred), and/or; c)attachment devices 8 and/or 9 should be self-sustaining, so that noapplied external action is needed to keep the pieces together once theyhave been initially attached.

In an embodiment, robot gripper 4 can be adapted to squeeze two or morespring-loaded latches in order to release the pieces.

In another embodiment, electromagnets in stage 7 can be adapted tointeract with permanent magnets in the latches in order to cause them torelease.

In a further embodiment, electromagnets in robot gripper 4 could releasepanel 3 by overpowering the magnetic attraction between permanentmagnets and targets respectively in both pieces of cover 102. Likewise,electromagnets in stage 7 could be temporarily energized to overcome themagnetic attraction between permanent magnets and magnetic targetsrespectively located in frame 102 and stage 7.

Many other embodiments are also possible, including but not limited topermutations and combinations of attachment features and placement ofthe release devices in the gripper instead of the stage or vice versa.All these permutations and combinations are contemplated within thescope of the present invention.

With continuing reference to FIG. 1, a variation of the above-describedembodiment can use gravity to keep reticle 1, frame 2, and panel 3together. Specifically, robot gripper 4 can support panel 3, frame 2 canrests on panel 3, and reticle 1 rests within frame 2. Correspondingfeature pairs 5 a and 5 b can align frame 2 to panel 3 and correspondingfeature pairs 6 a and 6 b can align panel 3 to robot gripper 4.

In various embodiments, feature pairs 5 a and 5 b and 6 a and 6 b can bechosen from a group including kinematic mounts (for example, with ballsin grooves or conical seats), dowel pins in holes and slots, and nestingone piece within the other. A device for energizing to holding andreleasing frame 2 from stage 7 can be located in stage 7, as shown inFIG. 1, or built into the robot gripper 4 instead.

According to another exemplary embodiment, two or more spring-loadedmechanical latches 9 located in stage 7 can be used to hold frame 2,through use of tabs 8, to stage 7, as shown and described below withrespect to FIGS. 2 and 3.

In further embodiments, the release of the latches can be achieved, forexample, by momentarily applying a magnetic force via solenoids 11,coupled to stage 7, to overcome a closing force applied by springs 10,thus retracting the latches, which can be made of a magnetic material.

Feature pairs 14 a and 14 b can be placed on a bottom side of panel 3and on other surfaces where system 100 (e.g., a reticle/cover assembly)has to be placed. For example, on vacuum library shelves and on standardmechanical interface (SMIF) pod baseplates, generically represented asitem 13, and described in more detail below.

FIG. 2 shows a state of reticle 1 and cover 102 according to anembodiment of the present invention. Thus, the state shown in FIG. 2shows frame 2 and panel 3 being loaded onto stage 7 using robot gripper4. In one embodiment, the state is when solenoids 11 have beende-energized and latches 9 have captured tabs 8. During this state frame2 in secured in place. This state can be prior to retracting robotgripper 4.

FIG. 3 shows a state of system 100 according to embodiments of thepresent invention. During the state, reticle 1 and frame 2 are supportedsolely by the stage 7 after robot gripper 4 (not shown in FIG. 3) hasretracted, carrying away panel 3 (not shown in FIG. 3). In someembodiments, lithographic exposure can begin at this point throughopening 14.

An embodiment where robot gripper 4 holds frame 2 instead of panel 3 canbe simpler, and therefore preferable to other embodiments. This isbecause gravity is exploited to keep panel 3 and frame 2 together. Thedownward motion of robot gripper 4 is substantially all that is neededto detach 3 panel from frame 2 after frame 2 has been captured by stage7.

Alternative embodiments that also facilitate alignment of reticle 1 tostage 7, and an explanation of a method used for alignment, aredescribed below.

As described elsewhere herein, reticle 1 should be placed and orientedconsistently with a wafer. This substantially ensures that a layer ofcircuitry being currently copied from a reticle pattern onto the waferwill line up with pre-existing layers on the wafer.

In several embodiments, described in more detail below, reticle 1 can betransported to the lithography system (or “litho tool”) in a container(e.g., a pod), a portion of which can be item 13. The pod can include aframe that supports reticle 1 and a panel that keeps contaminantparticles away from reticle 1 during transport. In these embodiments, abottom side of the pod frame can have locating features that correspondto matching locating features in the litho tool, such that theorientation of the SMIF pod relative to the litho tool is uniquelydetermined.

With reference again to FIG. 1, reticle 1 can be held securely in placeon a top side of frame 2 by a combination of resting points and stopsbuilt into frame 2 and springs built into panel 3. Since reticle 1 canbe a flat square with no special locating features, there may be eightways that it will fit within the nest formed by the resting points,stops and springs.

When loading reticle 1 into the pod, care should be taken to placereticle 1 with the patterned side facing in a desired direction (e.g.,right side up) and with a desired orientation (e.g., 90 degrees)relative to the pod. For example, a top edge of the pattern may betowards a front side of the pod. Then, the location and orientation ofreticle 1 relative to the litho tool can be known when the reticle podis placed in the litho tool. Typically the position (X,Y) uncertainty isin the order of about 1 mm (millimeter) and the angular orientation (θz)uncertainty is in the order of about 1 degree. However, this accuracy isnot sufficient for current lithography. The position uncertainty must bereduced to only several micrometers and the orientation uncertainty toless than 1 arc-second.

Thus, according to embodiments of the present invention a lithographytool can be equipped with a pre-aligner. The pre-aligner preciselypositions and aligns the pattern in reticle 1 to the lithography tool bylooking at targets on the reticle pattern and moving reticle 1 as neededto correct its position and orientation. Robot 4, or any other dedicatedtransfer mechanism, typically transfers reticle 1 from frame 2, to thepre-aligner and from the pre-aligner to stage 7. The transfer from thepre-aligner to stage 7 must be very accurate, since any positioningerrors introduced by the transferring devices will reduce the placementaccuracy of reticle 1 on stage 7. Hence, a very accurate and repeatablerobot or transfer mechanism should be used for the critical step oftransferring reticle 1 from the pre-aligner to stage 7.

Precision-movement robots can be located at a printing stage of thelithography system, which is adequate for deep ultra violet (DUV)lithography. However, this may not work for to EUV lithography becausethe EUV process must take place in vacuum. This is due to the totalabsorption of EUV light at normal pressures, as discussed above. Thus, avacuum-compatible robot must be used. Since motors and electronicsgenerate heat and outgas contaminants, which in a vacuum are verydifficult to remove, vacuum compatible robots are designed to have theirmotors and electronics outside the vacuum chamber. Inside the chamber,long mechanical linkages are used to transfer the motion to the objectbeing handled. This arrangement is clean and produces no heat inside thechamber but it suffers from inherently poor positioning accuracy andrepeatability due to the considerable length, low stiffness and “play”of the linkages. Hence, the available vacuum robots are inadequate forperforming the critical step of transferring the reticle from thepre-aligner to the stage. It is clear that an alternative solution thatwould make the accuracy and repeatability of the robot non-criticalwould be desirable.

FIG. 4 shows an embodiment of system 100 in which panel 3 can be usedfor accurate and repeatable positioning in the final transfer, henceallowing the use of cleaner and necessarily imprecise robots. A preciselocation of panel 3 relative to the pre-aligner can be achieved bykinematically docking panel 3 to the pre-aligner. Lower V-grooves 15 aengage with round-tip pins 15 b, which in one embodiment are located inthe pre-aligner. Lower half balls 6 a (see FIG. 1) can be similar to tippins 15 b and upper V-grooves 16 b can be similar to V-groove 15 a. Theuse of V-grooves 15 a and 16 b and round-tip pins 15 b and 16 a to dockobjects kinematically is well known, and there also exist otherwell-known designs of kinematic docks that are equally effective. Thepresent invention is not limited by the use of V-grooves and round-tippins, but can be implemented in principle with all known designs ofkinematic docks.

Robot gripper 4 can then picks the panel/frame/reticle assembly and moveit just below stage 7. Similarly, precise kinematic location of panel 3relative to stage 7 can be achieved by engaging upper V-grooves 16 b inpanel 3 with half balls 16 a in stage 7 when robot gripper 4 moves thepanel/frame/reticle assembly upwards. After panel 3 has kinematicallyengaged stage 7, latches 9 and an electrostatic chuck 17 can beenergized, respectively clamping frame 2 by tabs 8 and pulling reticle 1against stage 7. Robot gripper 4 can then move panel 3 downwards, andwithdraw with it, away from stage 7.

A property intrinsic to kinematic docks is that they can be repeatablewithin a few microns, only requiring that the initial alignment bewithin the capture range of the mating features. For example, thealignment of each half ball 16 a to each upper V-groove 16 b must besuch that each ball 16 a will initially contact any portion of thecorresponding groove 16 b. If this condition is met, then regardless ofinitial misalignment, the same final relative position will be reached.The capture range can depend on the size of the mating features. Forexample, using the feature sizes shown in FIGS. 1-4 a capture range ofplus or minus about 1 mm is easily achievable. Since this range islarger than the typical repeatability error of vacuum robots, theintended functional de-coupling can be achieved. It is necessary whenkinematically engaging panel 3 to stage 7 that robot gripper 4 becompliant in the (X,Y) plane, so as not to force a motion trajectoryestablished by robot gripper 4 upon the kinematic dock, but to let theinteraction of the docking features define the final trajectory. Theconsiderable length, low stiffness, and play in the robot linkage canprovide the small amount of compliance needed.

As discussed thus far, the embodiments of the present invention solvethe problem of accurately transferring frame 2 from the pre-aligner tostage 7 using a robot with accuracy and repeatability. For the transferto be useful, in addition, reticle 1 must remain in exactly the sameposition relative to panel 3 from the moment it is picked up from thepre-aligner to the moment chuck 17 is energized. One way to insure thiswould be to have the reticle 1 fit tightly within frame 2 and framelocating features 5 a have very tight clearances with theircorresponding locating features 5 b. However, this may not be the mostdesirable scenario because tightly fitting parts tend to produce manyparticles when pulled apart. Fortunately, in most of the embodiments ofthe present invention tight fits may not be needed because frictionbetween the parts is sufficient to keep them in place relative to eachother.

Due to the difficulties associated with motors inside a vacuum, andbecause suction gripping does not work in vacuum, vacuum-compatiblerobots can be designed to accelerate and decelerate just slowly enoughto enable the use of simple passive grippers that hold wafers on threepins purely by gravity and friction. Vacuum robot manufacturers providesubstantially no sliding using simple grippers.

Thus far, we have addressed the final transfer accuracy problem. Otherembodiments of the present invention show how cover 2 can alsofacilitate the task of aligning of reticle 1 to stage 7. In general, asstated above, a reticle coming into the tool in a pod can have apositioning error of about 1 mm and an orientation error of about 1degree relative to the panel. These errors can be reduced to a fewmicrons and less than about one arc-second. To do this, it is sufficientfor the pre-aligner to measure and correct the relative alignment andpositioning of reticle 1 to panel 3, since kinematic docking of thepanel to the stage has been shown above to be very accurate. Preferablythe re-positioning should be done without removing reticle 1 from frame2, so that no particles are generated on any reticle surface.

In various embodiments, a method for aligning reticle 1 to panel 3 issimplified by two-part cover 102. The robot brings thepanel/frame/reticle assembly to the pre-aligner, which is equipped witha set of round-tip pins 15 b. The assembly is thus docked kinematicallyto the pre-aligner by engaging lower V-grooves 15 a to round-tip pins 15b. Hence, panel 3 is precisely aligned and positioned relative to thepre-aligner. Therefore all that is necessary to precisely position andalign reticle 1 to panel 3 is to precisely position it and align itrelative to the pre-aligner. To do this, first the errors should bemeasured and then corrected.

According to one embodiment of the present invention, one way to measurethe errors is to equip the pre-aligner with a camera-based visionsystem, which can measure the angular and positional error betweentargets in the reticle pattern and targets permanently affixed to thepre-aligner and calibrated to the round-tip pins. Since the pattern ison the bottom side of reticle 1, the camera has to look through panel 3,which should be transparent at the wavelength that the camera operates.There are other well-known ways to measure the positional and angularerrors, and the present invention is not limited to using a camera and aset of targets.

In an embodiment, in order to correct the position and angularorientation of reticle 1 relative to the pre-aligner, the pre-alignercan be equipped with a precision manipulator having X, Y, Z and θzdegrees of freedom. The pre-aligner also can have a gripper capable oflifting frame 2 by engaging tabs 8 from below. The precision manipulatorwould first lift the frame/reticle just off panel 3, then effect the X,Y, and θz corrections and then lower the frame/reticle back onto panel3. At this point, reticle 1 is aligned relative to panel 3 and ready fortransfer to stage 7. Being able to re-position frame 2 relative to panel3 requires that there be ample clearance between positioning features 5a and 5 b.

It is to be appreciated that, since the vacuum robot is known to be ableto transfer objects without slippage, the various features pairs canincrease the accuracy for precise location. Additionally, the variousfeature pairs can be a safety feature to prevent gross accidentalsliding in case of abrupt robot stopping, which can be caused bycollision or power failure. In that event, precise alignment would belost, but the various features pairs would prevent reticle 1 fromfalling off robot gripper 4.

Finally, in embodiments used in a scanning lithography system with onelong range degree of freedom (for example it scans along the Y axis), itmay not be necessary for the pre-aligner to correct the position erroralong the degree of freedom coinciding with the scan axis of stage 7. Itmay only be necessary to measure the position error and communicate itto a stage controller, which can then compensate for the position errorby correspondingly offsetting the stage Y position during scanning.

Thus, in various embodiments, the various feature pairs can result in aprecision manipulator in the pre-aligner that has only one horizontaltranslational degree of freedom, X in the case of the example, as wellas Z and θz, which are still required. Thus, the design of the precisionmanipulator in the pre-aligner can be simplified for scanninglithography tools.

FIG. 5 shows a flow chart depicting a method 500 according to anembodiment of the present invention. Method 500 can be a method ofalignment and transfer using a two-part cover. In step 501, apanel/frame/reticle assembly can be kinematically docked to apre-aligner using a first set of feature pairs in the panel andcorresponding feature pairs in the pre-aligner. In step 502, thepositional and angular offsets of the reticle relative to thepre-aligner are measured. In step 503, the frame is manipulated tocorrect for the measured offsets, which re-positions the reticlerelative to the panel. In step 504, the panel/frame/reticle assembly ispicked up from the pre-aligner. In step 505, the panel/frame/reticleassembly is moved to the stage loading position with substantiallylittle relative slippage. In step 506, the panel/frame/reticle assemblyis kinematically docked to a stage using a second set of feature pairsin the panel and corresponding features in the stage. In step 507, thereticle and the frame are secured with clamping devices built into thestage (e.g., an electrostatic chuck and mechanical latches,respectively). In step 508, a panel us removed to expose the reticle.

As previously discussed, the embodiments of the present invention isuseful for substantially reducing particulate contamination generationwhen handling and aligning a reticle in an EUV tool. In conventionsystems that did not use a cover, reticle contact is made/broken eachtime the reticle is removed-from/replaced-in the SMIF pod, each time itis placed-in/removed-from the in-vacuum library, and each time it isloaded/unloaded at the stage.

According to embodiments of the present invention as discussed above andbelow, an improvement over conventional systems can be realized by usinga two-part cover. Contact between a reticle and a frame is never brokenbecause the frame remains in contact with the reticle even duringexposure. It has been assumed that the number of particles generated onthe reticle surface while handling the reticle varies directly with thenumber of times that mechanical contact with the reticle surface ismade/broken. By completely eliminating the need to make/break contactwith the reticle within the lithography tool, the two-part cover is asignificant improvement over a one-piece cover as taught in conventionalsystems, which merely reduces the number of particle-generating eventsdirectly involving the surface of the reticle, compared with directhandling of the reticle by the gripper.

The two-part cover according to embodiments of the present inventionalso allows the use of a soft material for contacting the reticlewithout much regard to durability of the soft material, since repeatedabrasive action is, in principle, eliminated. Using a well-chosen softmaterial presumably reduces surface damage and particle generationduring the initial placement of the reticle in the frame. A softmaterial such as a soft polymer, for example, may tend to flow, so as toconform to instead of scratching the delicate polished surface of thereticle.

In contrast, in conventional systems that do not use a two-part coverand that directly handling of the reticle with a robot gripper require ahard material in the gripper's contact points for acceptable durabilityof the gripper. The best hardness of the contact points of a one-partcover falls somewhere in between, since some contacting events stilltake place, but not as many. However, through the use the two-part coveraccording to embodiments of the present invention allows the two-partcover to be replaced when deformation leads to unacceptable precision.

The two-part cover according to embodiments of the present inventionalso facilitates pre-alignment of the reticle to the stage. This allowsfor precise final transfer from the pre-aligner to the stage even with alow-precision robot.

The two-part cover of the present invention also can be easier to keepclean than the robot gripper is. Whereas invasive maintenance isrequired to clean the robot gripper, which is located deep within thelithography tool and in vacuum, there is an opportunity to clean orreplace the cover much more conveniently each time the reticle isejected from the litho tool.

The present invention is described in terms of this example lithographyenvironment using a SMIF pod. Description in these terms is provided forconvenience only. It is not intended that the invention be limited toapplication in these example environments. In fact, after reading thefollowing description, it will become apparent to a person skilled inthe relevant art how to implement the invention in alternativeenvironments known now or developed in the future.

Therefore, according to embodiments of the present invention a systemand method are used to pseudo-kinematically register a reticle to aprotective cover. This can be done to maintain precise relative positionof the reticle during pre-alignment measurement and transfer to areticle stage. This can eliminate the need for mechanicallyre-positioning the reticle during pre-alignment of the reticle in thelithography tool. Secondly, it discloses a method of hardening thereticle contact areas so that they generate fewer particles when thereticle comes into contact with the cover.

FIGS. 6A and 6B show a two-part cover 102 according to embodiments ofthe present invention. Reticle 1 has edges 601 that can allow preciseregistration against registration features 602 against surface or wall603 in frame 2. In one embodiment, chamfering is performed on at least aportion of edges 601 of reticle 1 that contact the kinematicregistration features 602. In another embodiment, the portion of theedges 601 of reticle 1 are formed with a radius instead of a chamfer. Inyet another embodiment, an intersection of modified edge portions atcorners of reticle 1 produce a spherical or toroidal sector (an eighthof a sphere or of a toroid) in each corner, which then interfacesagainst a compatible registration feature 602 in each corner of frame 2.A user can choose which portions of the modified reticle edge 601 willbe contacted and which portions will be avoided.

With regard to registration features 602 in frame 2, placement is notlimited to the corners of the frame as shown in FIGS. 6A and FB.However, in a preferred embodiment this may be an advantageous location.For example, frame 2 could have registration features 602 in the middleof each side. It will also be apparent that the actual shape ofregistration feature 602 may be varied to best accommodate reticle edge601. For example, in one embodiment registration features 602 can be Vshaped grooves, with each surface 603 of groove 602 being flat. Thisparticular shape is suited for accommodating a radius at reticle edges601. It is to be appreciated that in other embodiments if reticle edges601 are chamfered they can be best accommodated by convex (instead offlat) groove surfaces in registration features 602.

According to one embodiment of the present invention, use ofregistration features 602 can obviate step 503 in FIG. 5. This is veryadvantageous, because a substantially complex pre-aligner mechanismwould be required in order to manipulate frame 2. By eliminating theneed to re-position frame 2 relative to panel 3, the design of thelithography tool is simplified.

FIG. 7 shows system 100 according to an embodiment of the presentinvention. Frame 2 can hold reticle 1 and can be kinematicallyregistered to panel 3 via a first set of kinematic registration featurepairs 701 a and 701 b. Similarly, panel 3 can be kinematicallyregistered to robot gripper 4 via a second set of kinematic registrationfeature pairs 702 a and 702 b. In addition, a third set of kinematicfeature pairs 703 a and 703 b can be used to kinematically registerpanel 3 to vacuum library shelves and SMIF pod baseplates genericallyrepresented by item 13.

In the embodiment shown in FIG. 7, kinematic features 702 a and 703 bshare the same groove, with 702 a interfacing to 702 b within theinnermost portion of the groove, and 703 a interfacing to 703 b withinthe outermost portion of the groove. It will be apparent to one skilledin the art that this relative placement could be reversed. It will alsobe apparent that separate grooves could be used to implement each ofthese kinematic features.

In another embodiment, a one-piece cover can be used. In thisembodiment, frame 2 can be secured to (e.g., glued or made from the sameblock of material as) panel 3 in order to create a one-piece cover. Theone-piece cover is entirely removed for lithographic exposure of reticle1. Therefore, feature pairs 701 a and 701 b may not be needed in thisone-piece cover embodiment.

Hardened Reticle

It is generally known that the EUV-reflective coating of reticle 1 canbe intrinsically delicate and soft. Thus, the coating can be prone togenerating particles whenever contacted. It would therefore be desirableto have designated areas devoid of EUV-reflective coating, which couldbe used for the purpose of supporting or handling reticle 1 by itsreflective side. To do this, a harder substrate material would thereforebe brought to the surface uncovered, henceforth “exposed.”Unfortunately, it appears to be practically very difficult to produceareas exposing the bare reticle substrate, henceforth “bare spots.” Oneknown method for producing bare spots is to use a mask that covers themduring the ion-beam sputtering process that is used to deposit theEUV-reflective coating. The problem with this approach is that due tothe nature of the deposition process, loose particles or flakes tend toform on the mask and break off when the mask is removed at the end ofthe process, with some particles or flakes landing on and contaminatingthe reticle. Another known method for exposing areas of the substrate isto selectively etch the EUV-reflective coating from the areas designatedfor handling. The problem with this approach is that the etching processalso tends to damage the remaining areas of the reticle.

It might also appear that the problem of supporting the reticle could besolved solely by using the radiused or chamfered edges as describedelsewhere in this disclosure. However, this is not true, since thefragility of the EUV-reflective coating dictates that the blanksubstrate must already have the edges machined to final shape beforecoating, and due to the uniform, non-selective coverage produced by thesputtering process that deposits the coating, the unmasked chamfered orradiused edges would also become coated with fragile material.

To solve the above-described problems, coating the EUV-reflectivematerial with a harder material has been proposed. The natural choicefor this material is the EUV-blocking layer that is deposited on top ofthe EUV-reflective layer and selectively etched, in order to create, or“write” the reticle pattern. Unfortunately, to have the correct opticalproperties, this layer must be very thin. A thin blocking layer on topof the soft reflective material is likely to break under the highhorizontal stress of mechanical handling contact. Adding and selectivelyetching a thick layer on top of the blocking layer is possible butcostly and unproven.

Therefore, what is needed is a process that can remediate the intrinsicsoftness and fragility of the reflective coating, without requiringmasking or removing of coating in order to create bare spots. What isalso needed is a method requiring neither bare spots in the selectedcontact areas nor covering the areas with an additional protectivelayer.

It is suspected that the intrinsic softness of the EUV-reflective layeris due to its multi-layered nature. As is known in the art, theEUV-reflective layer henceforth the “multi-layered structure” or simply“multi-layer” can include about 100 alternating layers of molybdenum andsilicon, each of the component layers being only about a few nanometersthick. Neither silicon nor molybdenum are normally soft materials.Therefore, according to embodiments of the present invention thesematerials can be locally melted together at desired contact spots totransform the soft multi-layer structure into a harder, uniform layer ofalloyed material. Purely for convenience, we will henceforth refer tothe process producing the local transformation of the multi-layer into aharder substance as “localized heat treatment”.

In some embodiments, it may not be necessary to completely melt themulti-layer in order to achieve the desired hardness. This is because itis known that heat causes each material in the multi-layer to quicklydiffuse into the other(s), thus forming a more homogeneous layer. Thismay occur even at temperatures well below the melting point of any ofthe multi-layer components. Hence, it will be apparent that localizedheat treatment can also be applied in order to transform the multi-layerinto a homogeneous layer by inter-diffusion instead of melting.

In other embodiments, deposition and diffusion of foreign substances ona layer can be used to strengthen the layer. Therefore, localizedheating of the contact area in the presence of foreign substances withthe intention of adding such substances to the layer is performed as theheat treatment process.

FIG. 8 shows a flowchart depicting a method 800 according to embodimentsof the present invention. Method 800 can be used for reinforcing areasin a reticle intended for handling contact by locally transforming amulti-layer-structured EUV-reflective coating. In step 802, an operationto coat the reticle substrate with an EUV-reflective multi-layerstructure (molybdenum-silicon or molybdenum-ruthenium-siliconmulti-layer, as is the present state of the art) is performed. In step804, an operation to locally heat treat the areas intended for handlingcontact, in order to transform the locally heated portions of themulti-layered structure into a stronger (harder, tougher) material isperformed.

In an embodiment, step 804 can be performed, for example, by focusing apowerful laser beam onto the designated areas of the reticle, possiblyin the presence of chemical substances, comprising reactive agents andcatalysts. Other types of radiative energy could be substituted for thelaser beam of the example. Other localized heating methods such as forexample inductive heating using a radio-frequency electromagnetic fieldcould also be used.

The low thermal conductivity of typical EUV reticle substrate materialsand of the multi-layer itself facilitate localizing the multi-layertransformation exclusively to the desired areas. This can be donewithout much fear of unintentionally altering the EUV-reflectivematerial within or near the patterned field of the reticle. Themulti-layer structure should remain intact in order to retain its uniqueoptical properties. Placement of the contact areas at the corners ofreticle 1 as suggested elsewhere in this disclosure maximizes theirdistance to the field, therefore making the effect of locally heattreating the contact areas most negligible as far as the opticalcharacteristics of the reticle's patterned field are concerned.

Substantially Flat Reticle Cover

FIGS. 9-11 show a reticle cover 902 according to embodiments of thepresent invention. Reticle cover 902, which is removable duringpredetermined events, protects a reticle (e.g., a mask) 901. Reticlecover 901, which can be transparent to certain wavelengths of light,comprises: support pads or spacers 903; nesting pins 904; kinematiclocators (e.g., mask locators) 905; and a hole 906. Hole 906 can be usedto allow injection of a pressurized gas sweep between cover 902 andreticle 901 and can comprise a gas filter. Various materials can be usedfor making pads 903 and pins 904, such that they do not damage reticle901 or shed particles when making or braking contact with it. Becausesome clearance is may be required between the reticle 901 and thenesting pins 904 for removing the cover 902, the reticle may slide asmall amount with respect to the cover 902. An improvement over theembodiments described above is that cover 902 is substantially flat. Byutilizing the substantially flat design less liquids are trapped duringcleaning because there are no pockets or cavities that can trap theliquid. Thus, cover 902 is easy to clean or “superclean.” In someembodiments, ultrasonic cleaning in a bath, rinsing, and spin dryingcleans cover 902. Thus, in contrast to conventional, complex covers thatwere very difficult to clean because of their configuration, cover 902is very easy to clean.

Double Wrapped Reticle Box (e.g., Reticle Pod)

FIGS. 12-13 show a side and an exploded view, respectively, of a reticlebox or pod 1250 (hereinafter, both are referred to as “pod”), accordingto embodiments of the present invention. More features of an example pod1250 are shown in FIG. 17, discussed in detail below. The pod 1250includes a possibly gas tight outer box 1252 having a base 1254 securedto a cover or lid 1256, which may be secured via a latch (not shown). Aplate 1258, similar to the cover 902 above, can be substantially flatwith no holes or cavities, which reduces production of particles andmakes cleaning of plate 1258 easier. Also, particle generation can befurther reduced by not requiring screws, or the like. A particle sealingdevice 1260 (e.g., an inner or first wrap) can be used to protectreticle 1 against particles and a gas sealing device 1262 (e.g., anouter or second wrap) can be used to make the outer box 1252 gas tight,which protects the inner or first wrap 1263 against molecularcontaminants. The particle sealing device 1260 engages before the gassealing device 1262 when the pod 1250 closes, and disengages after thegas sealing device 1262 when the pod 1250 can be opened. This can be incontrast to conventional systems lack both a gas sealing device, becausethey do not use vacuum, and a particle sealing device.

The outer box 1252 secures inside a gas-permeable inner capsule 1263,which protects against particulate contaminants and has detachable partsfor easy cleaning. The inner capsule 1263 includes a dome 1264 (e.g., aPyrex® glass dome) which can have thin walls (e.g. 2 mm) coupled to aplate 1266 (e.g., made from or coated with polyimide, ESD gradepolyetherimide, or the like). A reticle 1 and reticle cover 102 (e.g.,made from Pyrex® glass, or the like) are positioned inside the innercapsule 1263, which can interact with a robot gripper 1266. A device1268 (e.g., springs, or the like) can be used to couple the dome 1264 tothe lid 1256 and to apply restraining pressure to the inner capsule 1263for immobilizing the reticle 1 during transportation. This can alsocompress the particle sealing device 1260. A surface 1302 of the reticle1 can be glass, Crhomium-plated (e.g., Cr-plated), or otherwise platedwith a durable material. During use, the cover or lid 1256 of the pod1250 are removed to access the reticle 1. A filtered passage 1304 canconnect the volume included between the dome 1264 and the plate 1266 tothe remaining volume included within the pod 1250, allowing gas to flowbetween the two volumes, but preventing particle flow. An example of afiltered passage 1304 can be a hole through a wall of the dome 1264covered with a membrane gas filter, or the like. Another example can bea hole through the plate 1258 plugged with a sintered powder metal gasfilter, or the like. It can be to be appreciated other locations andfiltering devices can be used, as may be known in the art. Alignmentdevices 1306 can have polymide coated contact surfaces.

The above example materials used to manufacture the various parts of thepod 1250 reduce generation of particles. It can be to be appreciatedthat these materials are only being used as preferred examples, andother known materials can also be used.

The pod 1250 can be opened in two stages, as will be described in moredetail below with regards to the methodology of using the systems.First, the lid 1256 lifts a predetermined amount to break the gas sealcaused by the gas sealing device 1262. This causes gas to flow into thepod 1250, and particles to be transported with the gas. However,particles cannot reach the reticle 1 directly.

Gas flows through the filtered passage 1304, equalizing the pressureinside the dome 1264 to the ambient pressure. Second, as the lid 1256can be continuously lifted, the dome 1264 can be lifted off the plate1266. After the pressure inside the dome 1264 has been equalized toambient pressure in the previous step, there can be no significant flowof gas or particles in or out of the dome 1264 when it is lifted off. Inthese embodiments, either the dome 1264, the plate 1266, or both arepermeable to gas, i.e., they allow the flow of gas to eliminate apressure difference between inside and outside the dome 1264.

Loadlock

FIGS. 14-15 show side and exploded views, respectively, of a loadlockaccording to embodiments of the present invention. In one embodiment, areticle 1401 (that can be on top of support pins 1404) and a reticlecover 1402 are positioned between a base 1403 and a dome 1405. A domeremoving device (e.g., a dome lifter) 1406 comprises a motor 1407, alead screw 1408, and bellows 1409. The loadlock also comprises anopening 1410 for atmospheric side and vacuum side gate valves. All ofthe above parts are positioned inside an enclosure formed by a bottomsection (e.g., a vacuum shell) 1411 and a top section (e.g., a vacuumshell roof) 1412. The loadlock can also comprise a seal seatsubstantially conforming to an open end of the dome of the pod and/or aparticle sealing device for preventing particle flow between the domeand the seat. The loadlock can further comprise a filtered passage 1413that equalizes the gas pressure inside the dome with the gas pressureoutside the dome (e.g., a hole through the dome wall covered with amembrane gas filter) and a device (e.g., a sensor or detector) fordetecting airborne or gas borne (hereinafter, both are referred to as“airborne”) particles in the loadlock.

Typically, loadlocks are quite dirty, mainly because of gate valves thatseal to pump down or vent the loadlock. Each time the seal is made orbroken, particles are created that become air or gas borne. Also, thegate valves are complicated, mechanical assemblies with many moving,rubbing, friction causing parts and lubricants. This causes dirt toaccumulate inside the loadlock. During venting of a loadlock, gas flowsinto the loadlock and equalizes the pressure to atmospheric pressure,which causes movement of particles. Also, when pumping down theloadlock, gas flows out of the loadlock, which causes movement ofparticles. Therefore, by using encapsulation of the reticle inside thedome and plate, according to embodiments of the present invention, thereticle is protected from the particles.

Reticle Handler

FIGS. 16-17 show a reticle handler core 1701 and a reticle handlingsystem, respectively, according to embodiments of the present invention.The reticle handling system comprises a core environment (e.g., a vacuumand a mini environment) and an atmospheric (air) environment. The coreenvironment is substantially located in reticle handler core 1701. Withreference to FIG. 16, reticle handler core 1701 comprises a reticle 1601in a vacuum chamber 1602. Reticle 1601 is moved through vacuum chamber1602 via a vacuum robot 1603, which can have two arms. Reticle core 1701also comprises a gate valve 1604 between vacuum chamber 1602 and aprocess chamber. Reticle core 1701 further comprises a loadlock 1605having a loadlock turbo pump 1606 and loadlock gate valves 1607. Reticlecore 1701 still further comprises a de-podder 1608 that opens a pod1609. Openings in the loadlock and the de-podder connect to a clean gasmini-environment chamber 1610 and are accessible via a mini-environmentrobot 1611.

During operation, a reticle (not visible in this figure) is removed froman open pod 1609 by mini-environment robot 1611. The reticle is thenplaced inside loadlock 1605 through gate valve 1607. The loadlock ispumped down and the reticle is removed from the loadlock by vacuum robot1603. Reticle 1601 is transported through vacuum chamber 1602 usingrobot 1603 and placed through gate valve 1604 inside a process chamber(not shown in this figure). After processing, the vacuum robot 1603removes the reticle from the process chamber through gate valve 1604 andplaces it inside loadlock 1605 through gate valve 1607. The loadlock isthen vented and reticle 1601 is passed through loadlock 1605, from rightto left, before entering mini-environment chamber 1610. Mini-environmentchamber 1610 can be filled with clean, filtered, and/or dry gas (e.g.,dry nitrogen). Mini-environment robot 1611 then removes the reticle fromthe loadlock and places it in open pod 1609 located in de-podder 1608.The de-podder then closes the pod.

With reference now to FIG. 17, the reticle handler system also comprisesan air or atmospheric environment having an atmospheric robot 1702 usedto move pods 1703. Pods 1703 can be stored in a pod storage rack, asshown. Pods 1703 are typically handled using a bar or handle shownacross their top portions that an operator grabs and using various partsof its housing that the various robots engage. A pod elevator 1705,which is shown in an up position, elevates pods 1703 placed by anoperator in input location 1706 to the handling plane of robot 1702.Alternatively, pods 1703 can be delivered to the tool by an overheadtrack (not shown) which places pods 1703 in locations 1707 which can bereached directly by robot 1702. Robot 1702 is capable of moving pods1703 between upper elevator stop 1712, pod storage rack 1714, overheadlocations 1707, and/or de-podders 1609. Once a pod 1703 is placed in thede-podders 1609, reticle handler core 1701 opens the pod 1703 andprocesses the reticle 1601, as described in detail above. Similarly,after the reticle 1601 has been processed, reticle handler core 1701replaces the reticle 1601 in the pod 1703 and closes the pod 1703.Therefore, the work is divided between the reticle handler core 1701,which handles reticles 1601 outside pods 1703, and the atmosphericportion of the handler, which only handles pods 1703.

These two subsystems transfer handling of the reticle 1601 to each othervia the de-podders 1609. The reticle handler core 1701, which isdescribed in reference to FIG. 16, is also visible in this figure (FIG.17) and lies below the atmospheric robot 1702. To help orient thereader, vacuum chamber 1602, a mini-environment chamber 1610, de-podders1609, and a mini-environment robot 1611 are pointed out. There can bestorage capability in both the atmospheric environment and the coreenvironment.

In some embodiments, the filtered air environment can also comprise anidentification station for reading: an ID mark encoded on pods 1703, asmart tag attached to pods 1703, or the like.

In some embodiments, the gas mini-environment can comprise: (a) anidentification station for reading an ID mark encoded on a mask; (b) athermal conditioning station for equalizing the temperature of anincoming mask to a pre-determined processing temperature; (c) a maskinspection station, for detecting contaminants on at least one surfaceof a mask, a mask cleaning station; (d) for removing surfacecontaminants from at least one surface of a mask, and/or (e) a maskorienting station, for precisely orienting a mask relative to themachine. Also, in some embodiments, the mini-environment is purged witha gas selected from the group comprising: filtered dry air, syntheticair, a mix of dry nitrogen and dry oxygen, and/or dry nitrogen, or othergases.

In some embodiments, the vacuum portion comprises: (a) an identificationstation for reading an ID mark encoded on a mask; (b) a library fortemporarily storing at least one mask; (c) a thermal conditioningstation for equalizing the temperature of an incoming mask to apre-determined processing temperature; (d) a mask inspection station;(e) for detecting contaminants on at least one surface of a mask; (f) amask cleaning station, for removing surface contaminants from at leastone surface of a mask; (g) a mask orienting station, for preciselyorienting a mask relative to the machine; and/or (h) a processingstation, for processing at least one mask. In some embodiments, theprocessing station is for photolithographically reproducing a pattern ona surface of a mask onto a photoresist-coated wafer, using light. Insome embodiments, the wavelength of the light corresponds to an extremeultraviolet (EUV) portion of the spectrum and is between 10 and 15nanometers, preferably 13 nm.

Methodology

FIG. 18 shows a flowchart depicting a method 1800 for transporting amask, according to embodiments of the present invention. At step 1802, afirst portion of a mask is covered with a removable particle cover. Thiscreates a temporary mask-cover arrangement that protects the firstportion from being contaminated by airborne particles. At step 1804, asecond portion of the mask is left uncovered. At step 1806, thearrangement is enclosed inside a gas-tight box. The box can have amask-carrying portion and a lid, separable from the mask-carryingportion, for protecting the mask from airborne molecular contaminants.At step 1806, the arrangement inside the box is transported.

FIGS. 19A and 19B show two portions of a flowchart depicting a method1900 for transporting, handling, and processing a mask according toembodiments of the present invention. At step 1902, a first portion of amask is covered with a removable particle cover. This creates atemporary mask-cover arrangement to protect the first portion from beingcontaminated by gas-borne particles. At step 1904, a second portion ofthe mask is left uncovered. At step 1906, the arrangement is enclosedinside a gas-tight box. The box can have a mask-carrying portion and alid, separable from the mask-carrying portion, for protecting the maskfrom airborne molecular contaminants.

At step 1908, the box containing the arrangement is transported to aprocess tool. The process tool can have at least one of each of thefollowing components: a de-podder, a mini-environment chamber, amini-environment manipulator, a loadlock, a vacuum chamber, a vacuummanipulator, and a mask mount. At step 1910, the box containing thearrangement is placed on a first opening of a de-podder, such that thelid of the box prevents gas flow through the first opening. At step1912, the interior of the de-podder is purged with clean gas. At step1914, the box is opened by separating the mask-carrying portion from thelid, keeping the lid in place, for blocking gas flow, and moving themask-carrying portion and the arrangement to the interior of thede-podder. At step 1916, the arrangement is extracted from the de-podderthrough a second de-podder opening into a mini-environment chamber,using a mini-environment manipulator and placing the arrangement insidea loadlock through a first loadlock opening. At step 1918, the loadlockis pumped down. At step 1920, the arrangement is extracted from theloadlock through a second loadlock opening and moved to the interior ofa vacuum chamber using a vacuum manipulator. At step 1922, thearrangement is placed on a mask mount, such that the uncovered portionof the mask is in contact with the mount. At step 1924, the mount holdsthe mask. At step 1926, the cover is separated from the mask and removedor relocated using the vacuum manipulator. At step 1928, the mask isprocessed.

FIG. 20 shows a flow chart depicting a method 2000 for transitioning amask from atmospheric pressure to vacuum in a loadlock. In step 2002, amask is placed inside a loadlock. At step 2004, the mask is covered witha dome to prevent airborne particles in the loadlock from reaching themask. At step 2006, the loadlock is closed. At step 2008, the loadlockis pumped down. At step 2010, the loadlock is opened to vacuum. At step2012, the mask is uncovered by withdrawing the dome. At step 2014, themask is removed from the loadlock.

FIG. 21 shows a flowchart depicting a method 2100 for transitioning amask from vacuum to atmospheric pressure in a loadlock. In step 2102, amask is placed inside a loadlock. In step 2104, the mask is covered witha dome. The covering step 2104 is for preventing particles that becomeairborne inside the loadlock during subsequent venting and opening stepsfrom reaching the mask. In step 2106, the loadlock is closed. In step2108, the loadlock is vented. In step 2110, an atmospheric end of theloadlock is opened to an atmospheric environment. In step 2112, airborneparticles settle. In step 2114, the mask is uncovered by withdrawing thedome. In step 2116, the mask is removed from the loadlock.

FIG. 22 shows a flowchart depicting a method 2200 for transporting,handling, and processing a mask. In step 2202, a mask is enclosed insidea gas-tight box, having a mask-carrying portion and a lid, separablefrom the mask-carrying portion, for protecting the mask from airbornemolecular contaminants. In step 2204, the box containing the mask istransported to a process tool, having at least one of each of thefollowing components: (a) a de-podder; (b) a mini-environment chamber;(c) a mini-environment manipulator; (d) a loadlock; (e) a vacuumchamber; (f) a vacuum manipulator and a mask mount. In step 2206, thebox containing the mask is placed on a first opening of a de-podder,such that the lid of the box prevents gas flow through the firstopening. In step 2208, the interior of the de-podder is purged withclean gas (e.g., dry nitrogen). In step 2210, the box is opened byseparating the mask-carrying portion from the lid, keeping the lid inplace, for blocking gas flow, and moving the mask-carrying portion andthe mask to the interior of the de-podder. In step 2212, the mask isextracted from the de-podder through a second de-podder opening into amini-environment chamber, using a mini-environment manipulator andplacing the mask inside a loadlock through a first loadlock opening. Instep 2214, the loadlock is pumped down. In step 2216, the mask isextracted from the loadlock through a second loadlock opening and movingthe mask to the interior of a vacuum chamber, using a vacuummanipulator. In step 2218, the mask is placed on a mask mount. In step2220, the mask is processed.

In summary, during several of the above embodiments, a reticleencounters three environments: a pod environment (e.g., a purged dry gasmini-environment), a de-podder to loadlock environment (e.g., vacuum),and from loadlock to chuck environment. The reticle can be encapsulatedduring each environment transition. In some embodiments, a double wrappod is used by: opening the pod, purging the de-podder, waiting forairflow to stabilize, opening the capsule, and extracting the reticleand/or cover from the capsule. In other embodiments, a special designloadlock with dome is used by: placing the reticle and/or the cover in aloadlock, covering the reticle with a dome, venting to purge theloadlock, waiting for airflow to stabilize, lifting the dome, andextracting the reticle and/or the cover from the loadlock. In furtherembodiments, particle settling is prevented on patterned areas withoutusing a physical barrier by either controlling gas flow during pressuretransitions or filtering gas flow (curtain/barrier) on reticle frontside. In still further embodiments, the reticle is protected with aphysical barrier impervious to particles using a gas-permeable cover orthe reticle is stored inside pod with cover on, the reticle and coverare placed in a loadlock, the pressure transitioned with the cover on,and the cover removed once inside vacuum environment.

By using the above embodiments, particle generation is reduced even whenusing non-ideal materials for the various systems and parts of thesystems. This is accomplished, in part, through using protective frames,covers, etc., and using edge handling schemes.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to persons skilledin the relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. A system comprising: a box that holds a mask that is removeablysecured to a device with a separable lid; a first portion containingfiltered air at substantially first portion pressure; an first portionmanipulator that moves the box within the first portion; a de-podderused to transition the mask between the first portion and a gasmini-environment portion, the mini-environment portion being purged withclean gas at substantially first portion pressure and having amini-environment manipulator that moves the box within themini-environment portion; a loadlock that is used to transition the maskbetween the mini-environment portion and a vacuum portion; and a vacuummanipulator that moves the mask within the vacuum portion.
 2. The systemof claim 1, wherein the first portion manipulator places the box on thede-podder and removes the box from the de-podder.
 3. The system of claim1, wherein the mini-environment manipulator moves the mask within thegas mini-environment portion, removes the mask from the de-podder,places the mask inside the loadlock, and that removes a mask from insidethe loadlock.
 4. The system of claim 1, wherein the filtered airenvironment portion comprises one or more of: an elevator that acceptsthe box from a box input height beyond the reach of the first portionmanipulator and that vertically moves the box to within reach of thefirst portion manipulator; an identification station that reads an IDmark or a smart tag encoded on the box; and a storage rack thattemporarily stores the box.
 5. The system of claim 1, wherein the gasmini-environment portion comprises at least one of: an identificationstation that reads an ID mark encoded on the mask; a thermalconditioning station that equalizes the temperature of an incoming maskto a pre-determined processing temperature; a mask inspection stationthat detects contaminants on a surface of the mask; a mask cleaningstation that removes contaminants from the surface of the mask; and amask orienting station that orients the mask relative to the system. 6.The system of claim 1, wherein the gas mini-environment is purged with agas selected from the group consisting of filtered dry air, syntheticair, a mix of dry nitrogen and dry oxygen, and dry nitrogen.
 7. Thesystem of claim 1, wherein the vacuum portion comprises at least one of:an identification station that reads an ID mark encoded on the mask; alibrary that at least temporarily stores at least the mask; a thermalconditioning station that equalizes the temperature of the mask to apre-determined processing temperature; a mask inspection station thatdetects contaminants on a surface of the mask; a mask cleaning stationthat removes contaminants from the surface of the mask; a mask orientingstation that orients the mask relative to the system; and a processingstation that processes the mask.
 8. The system of claim 7, wherein theprocessing station is used to photolithographically reproduce a patternon a surface of the mask onto a photoresist-coated wafer using light. 9.The system of claim 8, wherein a wavelength of the light corresponds toan extreme ultraviolet portion of the spectrum.
 10. The system of claim8, wherein a wavelength of the light is between about 10 nanometers andabout 15 nanometers.
 11. The system of claim 8, wherein a wavelength ofthe light is about 13 nanometers.
 12. A system comprising: a firstportion having a first portion manipulator that moves a box within thefirst portion, wherein the box holds a mask that is removeably securedto a device with a separable lid; a de-podder portion that transitionsthe mask between the first portion and a gas mini-environment portion,the mini-environment portion having a mini-environment manipulator thatmoves the box within the mini-environment portion; a loadlock portionpositioned between the mini-environment portion and a vacuum portion,and through which the mask is transitioned.
 13. The system of claim 12,wherein the first portion manipulator places the box on the de-podderand removes the box from the de-podder.
 14. The system of claim 12,wherein the mini-environment manipulator moves the mask within the gasmini-environment portion, removes the mask from the de-podder, placesthe mask inside the loadlock, and removes a mask from inside theloadlock.
 15. The system of claim 12, wherein the first portioncomprises one or more of: an elevator that accepts the box from a boxinput height beyond the reach of the first portion manipulator and thatvertically moves the box to within reach of the first portionmanipulator; an identification station that reads an ID mark or a smarttag encoded on the box; and a storage rack that temporarily stores thebox.
 16. The system of claim 12, wherein the gas mini-environmentportion comprises at least one of: an identification station that readsan ID mark encoded on the mask; a thermal conditioning station thatequalizes the temperature of an incoming mask to a pre-determinedprocessing temperature; a mask inspection station that detectscontaminants on the mask; a mask cleaning station that removescontaminants from the mask; and a mask orienting station that orientsthe mask relative to the system.
 17. The system of claim 12, wherein thegas mini-environment is purged with a gas selected from filtered dryair, synthetic air, a mix of dry nitrogen and dry oxygen, or drynitrogen.
 18. The system of claim 12, wherein the vacuum portioncomprises at least one of: an identification station that reads an IDmark encoded on the mask; a library that at least temporarily stores themask; a thermal conditioning station that equalizes the temperature ofthe mask to a pre-determined processing temperature; a mask inspectionstation that detects contaminants on the mask; a mask cleaning stationthat removes contaminants from the mask; a mask orienting station thatorients the mask relative to the system; and a processing station thatprocesses the mask.
 19. The system of claim 18, wherein the processingstation is used to lithographically produce a pattern from a surface ofthe mask onto a wafer.
 20. The system of claim 18, wherein a wavelengtha wavelength used to lithographically produce the pattern comprisesextreme ultraviolet light.
 21. The system of claim 18, is between about10 nanometers and about 15 nanometers.
 22. The system of claim 18,wherein a wavelength a wavelength used to lithographically produce thepattern is about 13 nanometers.